for what it's worth, I don't find any of the distinctions offered to be significant. In most of the contexts spelled out below, 'moral' and 'ethical' could replace each other without changing the meaning. (I think the distinctions raised are artificial). But that's just one persons POV.
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MitchMar 28 '11 at 13:58

@Mitch: I think some of these distinctions are relatively modern ones invented by committees in corporations and institutions, conflicting with traditional usage in philosophy, where they are mostly synonymous. Note that Latin "mos" was taken as a literal translation of Greek "ethos" in Roman philosophy: "mos" then immediately gained the exact same connotations "ethos" had acquired over the centuries, even though these connotations were neither native to "ethos" in daily speech ("character, habit") nor to "mos" ("manner, habitual rule, habit") prior to their use in philosophy.
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CerberusMar 28 '11 at 14:23

5 Answers
5

You can be an ethical person without necessarily being a moral one, since ethical implies conformity with a code of fair and honest behavior, particularly in business or in a profession (an ethical legislator who didn't believe in cutting deals), while moral refers to generally accepted standards of goodness and rightness in character and conduct—especially sexual conduct (the moral values she'd learned from her mother).

Morals refer to an individual's beliefs about right & wrong, while ethics relate to those of a group. The example I'm most used to seeing is that while a lawyer likely regards murder as morally wrong, he's still ethically bound to do his best to defend the accused murderer. The morals are his own feelings, the ethics are from the professional group he belongs to.

In the philosophical sense, as I understand it, morals are the standards by which an individual or group determines what is and what is not correct or proper behavior and how one decides how to act, and ethics is the study of moral problems to determine how one should act, not how one does or thinks one should act.

A moral code is what one holds for oneself and at a high esteem, whereas the code of ethics is what is enforced upon a group for its general goodness.

The fact, one doesn't kill anyone can be his moral code whereas the non-compete agreements, that blocks an employee from working for a competition for a reasonable period of time, can a part of company's work ethic.

I quote 3 forum posts, written by the same user 'Jayson', which discuss the etymology, along with comparing these two words. I edit them lightly to improve readability.
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Mores is plural nominative of mos, which mos referred to custom or rule, the habitual manner in which a thing was done (essentially).

Ethos means pretty much the same exact thing; in regards to custom or habitual manner in which a thing was done.

The difference is that mos is Latin and
ethos is Greek.
So they are the same thing; they just ended up in our language, both, rather than just one.

Current English has them meaning slightly different things though.
Typically speaking; now, morals refer to your personal code of conduct regarding right and wrong while ethos tends to be used in common speak as a reference to the spirit of the code, or a code that embodies a central spirit or motivator.

And again, ethics tends to be used as an impersonal variation of morals.
For instance, in business classes, it is the ethics of a business.
At Church, it's your morals.

As to the meanings, ethikos is derived from ethos in the same way that "thoughtfulness" is derived from "thought" in English.
Ethikos generally meant something of, or relating to, morals, moral nature, or the expression of character.
Meanwhile, Ethos generally meant character, custom, habit, moral nature, abode, etc... as above, but directly rather than the "of, or relating to" concept.

Ethika is the feminine of Ethikos, and is so in use (meaning, you don't really see it in use as "ethikos" [neuter]) because Ethika is dependent on the person.
By that I mean "dependent" as in a "dependency", like children are to parents, or the color "red" is to "ball".

Anything that was not able to stand on it's own as a physical noun was, when flipped to an adjective at the very least, switched to the feminine as that was the gender for anything that was dependent upon another physical things stance.

So Ethika became Ethica, which became Ethic.

Mos was most likely derived from the Latin prefix ma- referring to "a measure of" in some form.
For instance...take a look at these Latin words:
Magus: a learned man (a measurement is being made on the character of the learning)
Magnus: powerful/extensive (a measurement is being made of the comparison regarding the character for strength, force, potency, and/or breadth)
Magister: master (a measure of character of the placement in social rank)
Macula: dishonor/blemish (a measure of character of the depreciation from the nominative of something)
Malus: bad/evil (similar to Macula, a measure of character of depreciation from the nominative of neuter stance regarding good/bad, righteous/evil)
Margo: a margin or border (a specific, yet relative measure of the boundaries that define the character of something)
Maturo: to hasten (a measure of speed increased in ratio relative to the nominative)
Maturus: maturity (a measure of growth in many forms, character, physical, spiritual, etc...)

Mos, then being a declension of Ma- root, is then a word that relates to the 'measure of the character' of something.

Meanwhile, Ethica was the custom, standard, habbit, or character of something, which would be the Mores employed in measure.

So if you were talking about your 'character' in measure, then it would be Mores.
If you were talking about the 'measure of character', then it would be Ethica.